Speaker 1: Welcome to brain stuff from how stuff works. Hey, brain stuff,
Speaker 1: Lauren Vogel bomb. Here, let's talk salt. You might toss
Speaker 1: a little over your left shoulder for good luck, sprinkle
Speaker 1: some on your eggs, or even tip a shaker into
Speaker 1: a frothy beer. However you use it, one thing's for certain.
Speaker 1: Most of us take salt for granted. Salt wasn't always
Speaker 1: such a simple matter. For centuries, it was a rare commodity,
Speaker 1: used as payment, as an impetus for wars, and often
Speaker 1: for survival. Salt preserved fish and ancient Egypt seasoned Roman
Speaker 1: salad dressings, and even came to stand for a measure
Speaker 1: of a person's integrity. A competent Roman soldier was worth
Speaker 1: his salt. He had earned his allowance of the valuable seasoning.
Speaker 1: But more than being tasty, salt kept entire civilizations alive
Speaker 1: thanks to its ability to prevent foods from turning into
Speaker 1: bacterial Latin killers. To understand how salt prevents foods from spoiling,
Speaker 1: it's important to first grasp how it's used to preserve foods.
Speaker 1: Salt is used in two primary ways, either in granual
Speaker 1: form or in brine form. A brine being a water
Speaker 1: and salt solution. A ham, for example, might be cured
Speaker 1: with salt, and cucumbers are preserved and turned into pickles
Speaker 1: with brine. Curing with salt granules, known as dry curing,
Speaker 1: means applying salt to the outside of a cut of
Speaker 1: meat and storing it for a couple of days up
Speaker 1: to several weeks. It's one of the most ancient ways
Speaker 1: of curing meats. Modern curing can involve injecting meat with
Speaker 1: salt brine. Whatever the form of salt it's used, the
Speaker 1: mineral preserves foods and makes them safer to eat by
Speaker 1: preventing bacteria from growing, including the bacteria that break down
Speaker 1: rotting food, and also food board pathogens such as salmonella,
Speaker 1: which can cause food poisoning, typhoid fever, and other serious problems.
Speaker 1: Salt inhibits bacteria in a variety of ways. It's a
Speaker 1: disruptor that reeks havoc in microbes, interrupting their enzymes and
Speaker 1: chipping away at their DNA. It most often works through dehydration,
Speaker 1: though removing many of the water molecules the bacteria need
Speaker 1: to live and grow. Water molecules and food are measured
Speaker 1: in terms of product water activity, a number that signifies
Speaker 1: the free water molecules present before salt preservation. Many fresh
Speaker 1: foods have point nine nine product water activity. The product
Speaker 1: water activity is lowered when salt dehydrates the food through
Speaker 1: the process of lasmosis. In essence, the salt around the
Speaker 1: outside of the food draws water molecules out and replaces
Speaker 1: them with salt molecules until the amount of salt is
Speaker 1: equal inside and out, Lowering the water product activity to
Speaker 1: point nine ford to point nine one is usually sufficient
Speaker 1: to prevent most bacterial growth. Today's episode was written by
Speaker 1: Laurie L. Dove and produced by Tristan McNeil. For more
Speaker 1: on this and tons of other salty topics, visit our
Speaker 1: home planet, how stuff works dot com.